Amorphous alloys are increasingly used in the fields of horology and jewellery, in particular for the following structures: watch cases, case middles, main plates, bezels, push-buttons, crowns, buckles, bracelets, rings, earrings and others.
Components for external use, intended to be in contact with the user's skin, must obey certain constraints, due, in particular to the toxicity or allergenic effects of some metals, especially beryllium and nickel. Despite the specific intrinsic properties of such metals, endeavours are made to market alloys containing little or no beryllium or nickel, at least for components likely to come into contact with the user's skin.
Zirconium-based bulk amorphous alloys have been known since the 1990s. The following publications concern such alloys:
[1] Zhang, et al., Amorphous Zr—Al—TM (TM=Co, Ni, Cu) Alloys with Significant Supercooled Liquid Region of Over 100 K, Materials Transactions, JIM, Vol. 32, No. 11 (1991) pp. 1005-1010.
[2] Lin, et al., Effect of Oxygen Impurity on Crystallization of an Undercooled Bulk Glass Forming Zr—Ti—Cu—Ni—Al Alloy, Materials Transactions, JIM, Vol. 38, No. 5 (1997) pp. 473-477.
[3] U.S. Pat. No. 6,592,689.
[4] Inoue, et al., Formation, Thermal Stability and Mechanical Properties of Bulk Glassy Alloys with a Diameter of 20 mm in Zr—(Ti, Nb)—Al—Ni—Cu System, Materials Transactions, JIM, Vol. 50, No. 2 (2009) pp. 388-394.
Amorphous alloys with the best glass forming ability, known as and referred to hereafter as “GFA”, and related to the critical diameter Dc* are found in the following systems:                Zr—Ti—Cu—Ni—Be,        and Zr—Cu—Ni—Al.        
The compositions (in atomic %) of the most frequently used/characterized alloys are listed below:                Zr44Ti11Cu9.8Ni10.2Be25 (LM1b)        Zr65Cu17.5Ni10Al7.5 [1]        Zr52.5Cu17.9Ni14.6Al10Ti5 (Vit105) [2]        Zr57Cu15.4Ni12.6Al10Nb5 (Vit106) and Zr58.5Cu15.6Ni12.8Al10.3Nb2.8 (Vit106a) [3]        Zr61Cu17.5Ni10Al7.5Ti2Nb2 [4]        
Given the allergenic potential of nickel, these alloys cannot be used for applications involving contact with skin, such as external watch parts or suchlike. Further, due to the toxicity of beryllium, the manufacture and machining of some of these alloys require special precautionary measures. This is a pity, because these two elements stabilise the amorphous phase, and make it easier to obtain alloys with a high critical diameter Dc*. Further, nickel has a positive effect on the corrosion resistance of zirconium-based amorphous alloys.
However, the critical diameter of nickel-free and beryllium-free zirconium-based amorphous alloys is generally lower than that of alloys containing nickel and beryllium, which is disadvantageous for producing solid parts. There is therefore a need to develop alloys that have a sufficient critical diameter Dc*.